Vibratory soil compacting apparatus

ABSTRACT

THE INVENTION IS CONCERNED WITH AN UNBALANCED CENTRIFUGAL FORCE GENERATOR FOR A VIBRATORY SOIL COMPACTING APPARATUS, THE GENERATOR COMPRISING A ROTARY SHAFT, A FIRST UNBALANCED ECCENTRIC MASS MOUNTED ON SAID SHAFT AT A FIXED DISTANCE FROM SAID SHAFT, A SECOND UNBALANCED ECCENTRIC MASS, MEANS MOUNTING SAID SECOND MASS ON SAID SHAFT FOR MOVEMENT RADIALLY THEREOF WHEREBY SAID SECOND MASS CAN MOVE RADIALLY OUTWARDLY CENTRIFUGALLY UPON ROTATION OF SAID SHAFT, AND SPRING MEANS OPPOSING SAID RADIAL OUTWARD MOVEMENT.

Sept. 21, 1971 R. PAPPERS VIBBATORY SOIL COMPACTING APPARATUS Filed June 24, 1969 INVEN TOR: Rudolf PAPPERS BY: m 0. w

his Afforney United States Patent Oflice 3,606,796 Patented Sept. 21, 1971 3,606,796 VIBRATORY SOIL COMPACTING APPARATUS Rudolf Pappers, Monchen-Gladbach, Germany, assignor to Bopparder Machinenbaugesellschaft m.b.H., am Guterbahnhof, Boppard am Rhine, Germany Filed June 24, 1969, Ser. No. 836,092 Claims priority, application Germany, June 29, 1968, P 17 84 029.8 Int. Cl. F16h 33/10 US. CI. 74-87 4 Claims ABSTRACT OF THE DISCLOSURE The invention relates to an unbalanced centrifugal force generator for a vibratory soil compacting apparatus.

In designing any new soil compacting apparatus it has hitherto always been necessary to determine the best cmpacting action by performing time consuming and costly experiments, which have necessarily been limited to only a few frequencies. Although experiments of this kind can indicate an optimal frequency for the unbalanced centrifugal force generator, the frequency determined in this way is in fact optimal only for certain particular types of soil. As soon as the soil compacting apparatus is used for compacting other types of soil, or for example rubble, that is to say materials of different granularity, moisture and the like, a different frequency is likely to be better, which again would have to be determined by further experimentation. The result in practice is that the frequency used is by no means the optimum.

Most of the known unbalanced centrifugal force generators operate at a constant frequency, generating a constant unbalanced centrifugal force. As explained above an apparatus limited in this way cannot satisfy the requirements over a wide range of operating conditions. In some known devices the frequency can be varied, involving however an increase or decrease of the unbalanced centrifugal force proportional to the square of the frequency. This kind of control is of little practical use, in the first place because the effect on the soil or rubble resulting from a change in frequency is entirely unpredictable, and secondly because with increasing frequency and an unbalanced centrifugal force which increases with the square of the frequency the parts of the apparatus can be stressed beyond the permissible limits.

Unbalanced centrifugal force generators are known in which, after the apparatus has been stopped, a part of the rotating eccentric mass can be adjusted in position relative to the rotary shaft of the apparatus, and relative to another part of the mass which is fixed in position relative to the shaft. The frequency can also be changed but only between two fixed values. An apparatus of this kind therefore still has only a limited range of applications.

Soil compacting machines are also known which are steplessly adjustable in regard to rotational speed and the distance between the unbalanced eccentric mass and the shaft. However this double adjustment is very costly and involves comparatively difficult manipulations by the operator. Machines of this kind have therefore not been successful in practice.

The object of the present invention is to provide a generator for a vibrating soil compacting apparatus which, within a limited speed range, allows the speed to be djusted while keeping the unbalanced centrifugal force constant. The amplitude decreases with the square of th rotational speed.

In accordance with the invention an unbalanced centrifugal force generator for a vibratory soil compacting apparatus comprises a rotary shaft on which are mounted a first unbalanced eccentric mass at a fixed distance from the shaft, and a second unbalanced eccentric mass the distance of which from the shaft is variable, the second mass being mounted relatively to the shaft in such a way that centrifugal force tends to move the second mass radially outwards, against the influence of a spring.

The outward movement of the unbalanced mass may be limited by an adjustable mechanical stop the distance of which from the axis of the rotary shaft is adjustable.

Preferably, a housing is mounted on the rotary shaft and contains the second mass which is guided in its radial movement by the inner walls of the housing, a helical compression spring acting between the second mass and a cover at the radially outermost end of the housing.

To give the adjustable second eccentric mass a smooth radial movement it is preferably damped, for example the housing can be filled with oil to act as a damper, the oil being expelled by the moving mass from one chamber into another through a gap provided for this purpose in the housing. Alternatively there can be a drilling, preferably of variable diameter, for example by the provision of inserts through the adjustable unbalanced mass, to give a dash pot effect.

One example of a generator constructed in accordance with the invention is illustrated in the accompanying drawings, which is an axial cross section.

A first unbalanced mass 3 is fixed to a rotary shaft 1 by a key 2, so that this first unbalanced mass is fixed in position relative to the rotary shaft, prevented from rotating relative to the shaft and prevented from moving toward or away from the shaft. In this example a wall 4 of a housing mounted on the rotary shaft is integral with the fixed unbalanced mass 3. The housing has a cover 5 containing an internal annular groove 6. The cover 5 is a tight fit on a flange 7 of the wall 4, forming an oil tight seal. A helical compression spring 8 is supported at one end in the groove 6, which acts as a retaining groove, preventing sideways movement. In cross section, that is to say in a plane parallel to the shaft 1 and perpendicular to the axis of the housing 4, the housing is circular to facilitate obtaining a good fit between the cylindrical housing 4 and a cylindrical unbalanced mass 9, which is capable of sliding radially in the cylindrical housing. The unbalanced mass 9 has an annular groove 10, opposite the annular groove 6 in the cover of the housing, for accommodating the other end of the spring 8. The housing is filled with oil, there being a drilling 11 allowing the oil to flow between one face and the other face of the adjustable unbalanced mass 9. The drilling or passage 11 may be of variable diameter provided in different inserts, one of which is shown at 9a.

This eccentric force generator allows variation of rotational speed, within certain limits, without any change, or with very little change in the resulting centrifugal force. The oil used for damping the movement of the adjustable unbalanced mass 9 also serves as a lubricant between the adjustable unbalanced mass and the inner wall of the cylindrical housing 4.

After removing the cover 5 of the housing, the adjustable unbalanced mass 9 and the spring 8 can easily be removed and replaced. Maintenance of the apparatus is therefore very simple. The dynamic characteristics of the apparatus can easily be changed by installing different 3 springs and different adjustable unbalanced masses. The spring can have a progressive or a regressive characteristic curve. Instead of a helical spring there can if desired be used dish springs, rubber springs, or pneumatic springs.

I claim:

1. In a vibratory soil compacting apparatus, an unbalanced centrifugal force generator comprising a rotary shaft, a first unbalanced eccentric mass mounted on said shaft at a fixed distance in a first direction radially from the axis of said shaft, a housing mounted on said rotary shaft in general alignment tranversely of the shaft with the first mass, said housing having a cylinder therein with its axis extending in a second direction, diametrically opposite the first direction, a second unbalanced mass mounted for reciprocation in the cylinder and functioning as a piston therein, yieldable means constantly urging the second unbalanced mass radially inwardly of the cylinder, and a liquid in the cylinder at least substantially filling the spaces in the cylinder radially inwardly and outwardly of the second mass, the parts being so constructed and arranged that the liquid can pass from one side of the second mass to the other upon the creation of a pressure difference between the liquid on said two sides of the second mass, whereby to damp the radial movements of the second mass.

2. The apparatus of claim 1, wherein the liquid is oil.

3. The apparatus of claim 1, wherein the second mass has an at least substantially axial passage therethrough to provide for the fiow of liquid from one side of the second mass to the other.

4. The apparatus of claim 3, comprising a replaceable insert in a second passage through the second rnass, said insert having the first recited passage extending therethrough, whereby the effective area of the first passage may be changed by substituting appropriate inserts with different sized first passages therethrough.

References Cited UNITED STATES PATENTS 2,286,770 6/l942 Symons 7461X 2,861,458 11/1958 Awedissjan 74-87 2,989,869 6/1961 Hanggi 746l 3,358,815 12/1967 Musschoot 74-61X JACOB L. NACKENOFF, Primary Examiner U.S. c1. X.R. 94-48 

